This invention relates generally to improved feed apparatus for automatic drills or the like. More particularly, but not by way of limitation, this invention relates to an improved rapid feed apparatus including yieldable stop apparatus located in the housing for stopping the rapid feeding movement of the spindle.
This invention is an improvement to the invention disclosed and claimed in U.S. patent application Ser. No. 547,702, filed 10/31/83 and assigned to the same assignee as this application.
One of the problems encountered in the use of automatic drills has been their inability to move the drill bit rapidly to the work piece and stop to prevent damage to the drill, the drill bit, or to the work piece. Rapid retraction of the drill bit is known as discussed hereinafter, but to applicant's knowledge, successful rapid feed for right-angle drills has not been previously accomplished. Successful rapid feed is important because it decreases production time for drilling a series of holes by almost one-half and, thus, increases production with a decrease in product cost.
In one apparatus manufactured in the past, a contact actuated valve is provided that engages a collar or other abutment on the spindle during the retraction movement, shifting the drill into automatic feed movement so that the drill continues to alternate between feed and retraction movement until the operator stops the drill. Also, it has been proposed to provide a stop on the spindle that engages the drill housing causing the drill motor to stall. Manifestly, this has not been very successful in that damage can occur to the various portions of the gear drive mechanism in the drill.
Feeding and retraction of automatic drills is normally accomplished through speed relationships as will appear hereinafter. Motor reversal in such drills is not required and, therefore, is not usually provided since drill bits are manufactured to cut or drill with rotation in one standard direction.
Accordingly, one object of this invention is to provide rapid feed apparatus for automatic feed drills wherein the feeding movement is stopped when the drill bit encounters the work piece or in the event that high torque loads are encountered during rapid feeding to prevent damage to the drill.